The present invention concerns the manufacture of tires. More precisely, it relates to the manufacture of reinforcements, in particular, for a tire crown.
It is known that tires are usually reinforced by monofilaments or cables or other assemblages of unitary strands, which will be generically designated by the term “reinforcement” in the present application. An important architecture parameter is the angle formed by those reinforcements in relation to a standardized reference well known to the experts, namely, the median plane perpendicular to the axis of rotation of the tire. The present invention pertains, notably, to reinforcements at zero degree, whatever the exact location of those reinforcements in the tire. The reinforcements can be made by depositing a single cord individually or by depositing several cords simultaneously, for example, a dozen parallel cords. The term “cord” as used herein refers without distinction to a single strand, like a monofilament, or to an assemblage of unitary strands, like a cable, and the term “reinforcement” refers without distinction to a single cord or a group of parallel cords. The cords can be bare or pre-coated with rubber or any other material capable of rendering the cords adhesive.
The state of the art contains numerous examples of use of zero degree reinforce-ments for reinforcing the sidewalls or the crown of tires. But such an arrangement has the major disadvantage that the tire blank in production no longer lends itself or lends itself poorly to shaping during the subsequent phases of tire manufacture.
In order to provide a solution to these problems of shaping, a well known technique consists of cutting the cords at zero degree into sections. It is appropriate to call the piece of cord lying between the cuts a “section.” U.S. Pat. No. 4,791,973 illustrates this technique. A tire containing a belt including zero degree cords is described there. The latter are not circumferentially continuous. A number of sections succeed one another along a perimeter.
As it is very difficult to cut a reinforcement in rapid procession at very high speeds, this principle leads to rates of laying zero degree reinforcements that are much too slow, particularly if only one cord at a time is deposited and not a group of parallel cords, winding the reinforcement on the blank being made while moving a reinforcement laying head transversely. If depositing a single ply is envisaged, for example, by winding said ply in one turn on the bare blank during its assembly, it is necessary to prepare the desired incisions on said ply in advance, and that method requires providing a welding overlap in order to ensure the recovery of circumferential tensile stresses.